End-capped unsaturated polyetherester, unsaturated polyester and vinyl monomer

ABSTRACT

A compositon useful as an intermediate for a skin laminate and a fiber-reinforced composite comprises:(A) At least 5 wt. % of an at least partially end-capped unsaturated polyetherester wherein the end-capping compound includes a compound having at least one epoxy group;(B) an unsaturated polyester resin such that the weight ratio unsaturated polyester resin (B):polyetherester resin (A) is from about 10:90 to about 90:10;(C) from about 10 to about 70 wt. % of at least one vinyl monomer such as styrene; and(D) a curing agent such as a free radical initiator and an accelerator.

This application is a divisional of Application Ser. No. 09/168,493filed Oct. 8, 1998, abandoned, which claims benefit of Ser. No.60/062,112, filed Oct. 14, 1997, and claims benefit of Ser. No.60/062,852, filed Oct. 10, 1997.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention pertains to the field of resin systems including curablethermoset resins, composite materials and skin laminates for compositematerials, and processes for making the same.

2. Description of Related Art

Known gel coated fiber-reinforced polymers are subject to blistering ifimmersed in water or solvents for a prolonged period of time unlessspecial measures are taken to prevent this phenomenon. Blisters areraised by localized swelling of the gel coated laminate due to diffusionof water into the composite and the presence of water-solubleconstituents within the laminate. The blisters not only effect theexternal appearance of the gel coated fiber-reinforced polymer article,but also eventually lead to reduced composite strength.

Several methods have been proposed to reduce blistering in gel coatedcomposite materials. U.S. Pat. No. 4,724,173 describes using a permeablegel coat to allow the osmotically active molecules to diffuse from theosmotic centers through the gel coat at a defined transport rate wherebythe osmotic pressure of the osmotic centers is reduced so as to reduceblistering. U.S. Pat. No. 4,477,325 describes a method of manufacturinga skin barrier which has improved water resistance to protect thecomposite material from hydrolysis. U.S. Pat. Nos. 4,480,077 and4,525,544 describe vinyl ester resin compositions which may be used inthe laminate construction to impart greater resistance to waterpermeation and U.S. Pat. No. 4,959,259 describes a bisphenolic polyesterresin composition which may also be used to impart greater waterpermeation resistance.

The latter technique, using a laminate resin having greater corrosionand/or water resistance, is the most common technique used by thecomposite industry to reduce blistering. Those resins are typicallyvinyl ester resins or isophthalic polyester resins. Not only is thattechnique not always completely successful, it also increases theoverall expense of the composite material and/or reduces the flexibilityin choosing the laminating resin for other desired properties.

For these and other reasons, further improvements in the ability toprevent blistering are desired. These and other objectives are achievedby the present invention.

SUMMARY OF THE INVENTION

One aspect of this invention is curable thermoset resin compositionsuseful for imparting water and/or solvent resistance to gel coatedfiber-reinforced polymers comprising:

(A) At least 5 wt. % of an at least partially end-capped unsaturatedpolyetherester resin;

(B) An unsaturated polyester resin having a ratio of the number averagemolecular weight to the average number of double bonds per polymermolecule in the range from about 200 to about 400, in an amount suchthat the weight ratio of polyester resin (B) to polyetherester resin (A)is in the range from about 10:90 to about 90:10;

(C) About 10 to about 70 wt. % of at least one vinyl monomer; and

(D) A curing agent.

Another aspect for this invention is a method for making a curablethermoset resin compositions comprising combining:

(A). At least 5 wt. % of an at least partially end-capped unsaturatedpolyetherester resin;

(B) An unsaturated polyester resin having a ratio of the number averagemolecular weight to the average number of double bonds per polymermolecule in the range from about 200 to about 400, in an amount suchthat the weight ratio of polyester resin (B) to polyetherester resin (A)is in the range from about 10:90 to about 90:10;

(C) About 10 to about 70 wt. % of at least one vinyl monomer; and

(D) A curing agent.

A further aspect of this invention is an intermediate for making acurable thermoset resin composition comprising

(A) At least 5 wt. % of an at least partially end-capped unsaturatedpolyetherester resin;

(B) An unsaturated polyester resin having a ratio of the number averagemolecular weight to the average number of double bonds per polymermolecule in the range from about 200 to about 400, in an amount suchthat the weight ratio of polyester resin (B) to polyetherester resin (A)is in the range from about 10:90 to about 90:10; and

(C) About 20 to about 50 wt. % of at least one vinyl monomer.

DETAILED DESCRIPTION OF THE INVENTION

Definitions

The term “end-capping compound” as used herein means a compound havingat least one functional group capable of reacting with at least onereactive end group of the unsaturated polyetherester resin such that theacid number of the unsaturated polyetherester resin is reduced. When theend-capping compound has more than one functional group per molecule,then the functional groups are selected such that they have, under thesame conditions, a greater propensity to react with a reactive end groupof the unsaturated polyetherester resin than with another functionalgroup of the end-capping compound to avoid substantial polymerization ofthe end-capping compound with itself. The functional groups of theend-capping compound are preferably the same, or are known to besubstantially unreactive with each other.

The term “curing” and “cured” refer to the formation of a substantiallyirreversible three-dimensional crosslinking network in a curable polymercomposition such that the polymer forms a structure that issubstantially insoluble in solvents for the uncrosslinked polymer.

The term “bisphenol-A” refers to 2,2-bis(4-hydroxyphenylpropane).

The term “unsaturated polyetherester resin” means polymer resins ofintermediate molecular weight that contain ethylenic unsaturationavailable for free-radical polymerization with a vinyl monomer,recurring ester units, and recurring polyether blocks. The polyetherblocks have repeat units of oxyalkylene groups (-O-alkylene-), which ina preferred embodiment have from 2 to 10 carbon atoms each (e.g.,oxypropylene, oxyethylene, etc.), more preferably from 2 to 4 carbonatoms. Preferably, the unsaturated polyetherester resins have anether/ester mole ratio of at least about 0.75, more preferably at leastabout 1 and preferably not greater than about 3. The number averagemolecular weight of these resins is preferably in the range from about500 to about 10,000. They have alcohol and/or carboxylic acid end groupswhich react with at least one of the end-capping compounds.

Unless otherwise specified herein, the term “viscosity” refers to theviscosity of a polymer in styrene monomer at 65 wt. % NVM (non-volatilematerial, see below) at 25 C. measured using a Brookfield Viscometer.

The term “NVM” refers to non-volatile material (a.k.a. “solids”)dispersed in a volatile substance (e.g., styrene monomer) measuredaccording to ASTM D1259.

The term “ASTM” refers to a well known collection of standard laboratoryprocedures for measuring the properties of materials published by theAmerican Society for Testing and Materials.

Unless specified otherwise, all ratios, percentages, and parts are byweight.

A more detailed description of each component of the curable thermosetresin composition follows.

COMPONENT (A)

Suitable unsaturated polyetherester resins for making the correspondingend-capped resins include the reaction products of polyethers andunsaturated carboxylic anhydrides or unsaturated di-or polycarboxylicacids. Preferred polyethers include polyether polyols, such aspolyoxyalkylene polyols, alkylene oxide-alkylene oxide copolymers, andthe like, in which the alkylene group preferably has from 2 to 6 carbonatoms (for example, polyoxypropylene polyols, polyoxyethylene polyols,ethylene oxide-propylene oxide copolymers, etc.). These polyolspreferably have average hydroxyl functionality in the range from about 2to about 8 and preferably have a number average molecular weight in therange from about 250 to about 10,000. The unsaturated anhydrides arepreferably cyclic anhydrides, such as maleic anhydride, succinicanhydride, phthalic anhydride, and the like. Preferred unsaturated di-orpolycarboxylic acids include linear, branched, and cyclic C₃-C₄₀dicarboxylic acids and C₈-C₄₀ aromatic dicarboxylic acids, such asmaleic acid, fumaric acid, phthalic acid and isophthalic acid.

U.S. Pat. No. 5,319,006, which is incorporated herein by reference,describes one process for making the unsaturated polyetherester resinsin which the polyether is reacted with a cyclic unsaturated carboxylicanhydride in the presence of a Lewis acid catalyst.

U.S. Pat. Nos. 5,436,313 and 5,436,314, also incorporated herein byreference, describe preferred methods for preparing the unsaturatedpolyetherester resins in which the catalyst for inserting anhydrides anddicarboxylic acids into the polyethers are protic acids having a pKaless than about 0 and metal salts thereof.

The unsaturated polyetherester resins are end-capped with at least oneend-capping compound such that the end-capped resin has a lower acidnumber than the resin prior to end-capping. Preferably the acid numberis decreased by at least 50 percent.

The end-capping compound may, for example, be dicyclopentadiene, anepoxy-containing compound or both.

The epoxy group-containing compound may be represented by the followingformula:

wherein R¹, R² and R³ represent a hydrogen atom or a hydrocarbyl groupoptionally having one or more hetero atoms, provided that at least oneof R¹, R², and R³ is not a hydrogen atom. The hydrocarbyl group may bemethyl, aliphatic, cycloaliphatic, or aromatic, combinations of two ormore of methyl, aliphatic, cycloaliphatic and aromatic moieties, with orwithout hetero atoms. The hetero atoms may, for example, be oxygen orsulfur atoms present as ether or ester linkages between two or moremethyl, aliphatic, cycloaliphatic, or aromatic moieties and/or thehetero atoms may be present in functional groups, such as additionalgroups of formula (VI). The hydrocarbyl group preferably does notcontain functional groups reactive with the epoxy group on formula (VI).Preferably, the epoxy-containing compound has at least two hydrocarbylgroups that do not contain moities reactive with the polyetheresterresin (A).

The number average molecular weight of the epoxy-containing compound ispreferably no greater than 1500, preferably no greater than about 1000,and even more preferably no greater than 500. The epoxy group-containingcompounds include, for example, glycidyl esters, glycidyl ethers, epoxyalkyls, epoxy cycloalkyls, epoxyalkylenes, aromatic epoxy compounds,such as p-glycidyl-styrenes, and the like, and mixtures thereof.Specific examples of the epoxy group-containing compounds includeCARDURA® Resins (glycidyl esters available from the Shell Oil Company)such as CARDURA® E-10 Resin (a glycidyl ester of Versatic™ 10 Acid;GLYDEXX® available from Exxon Chemical Co., such as GLYDEXX® N-10 orND-101; etc.

Suitable aromatic epoxy compounds include glycidyl ethers obtainable bythe reaction of epichlorohydrin with an aromatic compound containing atleast one hydroxyl group carried out under alkaline reaction conditions.The epoxy-containing compounds obtained when the hydroxylgroup-containing compound is 2,2-bis(4-hydroxy-phenylpropane) (i.e.,bisphenol-A) are represented by the structure below wherein n is zero ora number greater than 0, commonly in the range of 0 to 10, preferably inthe range of 0 to 2.

Other suitable epoxy compounds can be prepared by the reaction ofepichlorohydrin with mononuclear di- and tri-hydroxy phenolic compoundssuch as resorcinol and phloroglucinol, selected polynuclear polyhydroxyphenolic compounds such as bis(p-hydroxyphenyl) methane and4,4′-dihydroxybiphenyl, or aliphatic polyols such as 1,4-butanediol andglycerol.

Preferred diepoxy compounds include those designated EPON® Resincommercially available from the Shell Oil Company, such as EPON® Resins825, 826 and 828, each of which are reaction products of epichlorohydrinand bisphenol A in which the n value of the above formula is 0.04, 0.08and 0.13, respectively. The commercially-available epoxy resin EPON®Resin 828 having a molecular weight of about 400 and an epoxideequivalent (ASTM D-1652) of about 185-192, is a preferred diepoxycompound because of its low viscosity, mechanical performance andcommercial availability.

Additional examples of suitable bisphenol-A type epoxy compounds includethe D.E.R.™ resins available from The Dow Chemical Company, such asD.E.R.™ 330, 331, 332 and 383 and the ARALDITE™ GY resins available fromCiby-Geigy such as ARALDITE™ GY 6004, 6005, 6008, 6010 and 2600.

In a preferred embodiment, the at least one end-capping compoundcomprises at least some, more preferably at least about 20 wt. %, evenmore preferably at least about 50 wt. % and preferably less than orequal to about 80 wt. %, DCPD and/or monofunctional epoxy-containingcompound, which may be obtainable by reacting the same with theunsaturated polyetherester resin in the corresponding proportions. Inone embodiment, the at least one end-capping compound comprises amixture of (a) DCPD and/or monofunctional epoxy-containing compound and(b) a di-or polyfunctional epoxy-containing compound, preferably whereinthe ratio of (a) to (b) is in the range from about 10:90 to about 90:10,more preferably from about 20:80 to about 80:20. In addition to theother advantages of this invention, curable thermoset compositionscontaining these end-capped unsaturated polyester resins also have theadvantage of ease of application due to the low viscosity of suchresins. In a preferred embodiment, the viscosity of the end-cappedunsaturated polyetherester resin does not exceed 1500 cp (1.5 Pa.s), andthe viscosity of the curable thermoset composition preferably does notexceed 500 cp (0.50 Pa.s)

The at least partially end-capped unsaturated polyetherester resin ispresent in the curable thermoset resin composition in an amount of atleast 5 wt. %, preferably at least about 10 wt. % up to about 80 wt. %,more preferably up to about 60 wt. %.

COMPONENT (B)

Dicyclopentadiene (DCPD) polyester resins suitable as component (B) arepreferably derived from dicyclopentadiene, maleic anhydride and apolyhydric alcohol, preferably a glycol (e.g., propylene polyhydricalcohol, ethylene polyhydric alcohol, diethylene polyhydric alcohol,dipropylene polyhydric alcohol, or mixtures of these). The reaction ispreferably performed in the presence of water under conditions togenerate maleic acid from the maleic anhydride so as to formdicyclopentadiene maleate and then esterifying the maleate with theglycol to form the unsaturated polyester resin. The DCPD unsaturatedpolyester resin preferably has a viscosity not greater than about 500 cp(0.50 Pa.s).

The preparation of DCPD polymer resins is described, for example, inU.S. Pat. Nos. 3,933,757; 3,347,806; 3,883,612; 4,029,848; 4,148,765;4,348,499; and 4,246,367, the teachings of which are incorporated hereinby reference.

DCPD polyester resins are typically available as solutions in vinylaromatic monomers such as styrene. To the extent that the vinyl aromaticmonomer is already introduced by the DCPD polyester resin solution, thatcounts towards the presence of vinyl monomer component (C).

The proportion of DCPD polyester resin to polyetherester resin fallswithin a weight ratio range of about 10:90 to about 90:10, andpreferably within the range from about 25:75 to about 75:25.

COMPONENT (C)

The vinyl aromatic monomers useful as component (C) of this inventioninclude styrene, vinyl toluene, cholorostyrenes, tert-butylstyrene,dimethylstyrenes, divinylbenzene, diallylphthalate, mono- ormultifunctional lower alkyl esters of acrylic and methacrylic acids, andthe like, and mixtures thereof. Styrene is preferred. The vinyl aromaticmonomer is present in an amount effective to result in a cured thermosetwhen reacted with the other components of the curable thermoset resincomposition in the presence of a free-radical initiator. The amount ofvinyl aromatic monomer in the curable thermoset resin composition is inthe range from about 10 to about 70 wt. %. Preferably, the vinyl monomeris present in an amount of at least about 20 wt. %, more preferably atleast about 30 wt. %, up to about 60 wt. %, more preferably up to about50 wt. %, and even more preferably up to about 36 wt. %.

COMPONENT (D)

The curing agent (D) comprises at least one free-radical initiator.Useful free-radical initiators are those well known and commerciallyavailable in the unsaturated polyester industry. They include peroxideand azo-type initiators. Peroxide initiators include, for example,methylethyl ketone (MEK) peroxide, benzoyl peroxide,tert-butylperbenzoate, ter-butylperoxide, and the like, and mixturesthereof. The initiator is used in an amount effective to react the vinylaromatic monomer and other polymer components of the curable thermosetresin composition to produce a cured thermoset. Typically, the amount iswithin the range from about 0.5 to about 3 wt. %, more preferably fromabout 1 to about 2 wt. %, based on the weight of the curable thermosetresin composition.

An accelerator is often combined with the free-radical initiator in thecuring agent to allow curing at lower temperatures. Examples ofaccelerators include dimethylaniline and salts of transition metals(cobalt, iron, mangenese, copper, zinc, or vanadium), such as cobaltnaphthenate, cobalt octanoate, and the like.

Optional Ingredients

Further components may be added to the curable thermoset resincompositions of this invention. Such components include reenforcingagents such as fibers, for example glass, fibers or organic fibers,which may be in chopped form or in the form of a fabric or mat; fireretardants (phosphorous or antimony compounds, aluminum trihydrate,halogenated waxes, etc.), antioxidants, free radical initiatorinhibitors (e.g., to prevent premature initiation of polymerization),pigments, colorants, mold release agents, inert fillers (calciumcarbonate, clays, talc, etc.), low-profile or low-shrink additives,thickeners (magnesium oxide, magnesium hydorxide, calcium oxide, etc.),etc. When reinforcing fiber is used, the amount of fiber is preferablyat least 5 wt. %, more preferably at least about 10 wt. %, up to about80 wt. %, more preferably up to about 60 wt. %, of the total weight ofthe composition.

Utility of the Curable Thermoset Resin Composition

The curable thermoset resin compositions of this invention, whencombined with a reinforcing fiber may be used to obtain afiber-reinforced polymer composite by curing the thermoset resincomposition.

The curable thermoset resin composition of this invention may also beused to prepare an intermediate for making a skin laminate by combiningthe curable thermoset resin composition with reinforcing fibers in theform of a sheet preferably having an average cross-sectional thicknessof at least about 10 mil (0.25 mm), more preferably from about 20 mil(0.5 mm) up to about 200 mil (5 mm), more preferably up to 100 mil (22.5mm), even more preferably up to 30 mil (0.8 mm). The fiber content ofthe skin laminate is preferably in the range from about 25 to about 45wt. %. The fiber is preferably about 0.5 inch to about 2 inch (about 1to about 5 cm) chopped fiber or a shear of a continuous strand fibermat. The skin laminate intermediate may be used between a gel coat layerand a fiber-reinforced polymer layer in a gel coated polymer laminate toimprove water and/or chemical resistance and also to improve the surfaceappearance of the laminate.

Water and/or chemical resistance of the gel coated polymer laminate mayalso be improved by interposing just the curable thermoset resincomposition, with or without optional components, between the gel coatlayer and the fiber-reinforced polymer layer.

An advantage of interposing the thermoset resin of the present inventionbetween a gel coat layer and the fiber-reinforced polymer layer is toprevent blistering due to the migration of water and/or other lowmolecular weight substances, such as organic solvents, through the gelcoat into the fiber-reinforced polymer, causing swelling, delamination,and other problems in the fiber-reinforced polymer layer. The swellingcan cause a blister under the gel coat and continued migration of waterand/or other solvents into the fiber-reinforced polymer can eventuallylead to loss of strength in the fiber-reinforced polymer laminate.

In one embodiment, blistering of a gel coated fiber-reinforced polymeris reduced by applying at least one layer of the curable thermoset resincomposition or the skin laminate intermediate between the gel coat layerand the fiber-reinforced polymer layer and curing the curable thermosetresin composition. Preferably, this is carried out by applying a gelcoat composition to a mold, at least partially curing the gel coatcomposition, applying at least one curable thermoset resin compositionor the skin laminate intermediate to the at least partially cured gelcoat, at least partially curing the curable thermoset resin composition,applying at least one fiber-reinforced polymer layer to the at leastpartially cured thermoset resin composition layer, and curing theresulting product to form the gel coated fiber-reinforced polymer.

The polyester resin used to make the fiber-reinforced polyester resinmay be any general purpose polyester resin known in the art, such asorthophthalic acid-based polyester resins. Preferred polyester resinsare are those with a molecular weight/double bond or vinyl group (—C═C—)factor between about 150 and about 500, more preferably between about200 and about 350 (as further described in U.S. Pat. Nos. 3,701,748;4,295,907; and 5,637,630 which are incorporated herein by reference).These resins are made from a reaction of one of more glycols with anunsaturated dicarboxylic acid or its anhydride or with a mixture of theunsaturated acid or its anhydride with a saturated dicarboxylic acid orits anhydride. The reaction mixture may also include dicyclopentadieneto control the molecular weight of the polyesters as described in U.S.Pat. Nos. 3,883,612 and 3,986,922, which are incorporated herein byreference. The unsaturated polyester resin typically has a numberaverage molecular weight in the range from about 500 to about 5,000,preferably in the range from about 700 to about 2,000. Examples ofsuitable unsaturated polyester resins include the STYPOL® polyesterresins made by Cook Composites & Polymers, Inc. The polyester resin isapplied as a matrix precursor and then cured, for example,by using acuring agent described above for the polyetherester resin.

The gel coat composition may be any of those that are well known andavailable in the art. The gel coat is typically 10 to 25 mils (0.2 to0.6 mm) in thickness, and is the surface coating of the molded part. Thegel coat provides the finishing color and surface profile of the part.Gel coats are well known and various grades are commercially available.The selection of gel coat will depend upon the desired characteristicsof the part relative to, among other things, weatherability, hydrolyticstability, and surface finishing. Examples of commercially available gelcoat materials include gel coat materials available from Cook Compositesand Polymers under the marks POLYCOR®, ARMORCOTE®, BUFFBACK®,ENVIROCOR®, and LOVOCOR®.

Examples of the various types of reinforcement fibers that can be usedin the practice of this invention are glass fibers, carbon fibers,various aramid fibers, and other types of natural and synthetic fibers.The typical fiber content of the composite is between about 10 and 80percent by weight.

The composite and the molded part can, and often are, constructed in oneoperation. First, a gel coat is usually applied to the surface of themold, at least partially cured, and then a skin laminate is applied overthe at least partially cured gel coat. These are open mold operations.Then the fiber-reinforced polyester matrix precursor is applied, forexample,by hand lay-up or spray-up, or the fiber reinforcement isapplied to the skin laminate, the mold is closed, and the polyestermatrix precursor is injected into the closed mold, preferably with theclosed mold under vacuum. The precursor is then allowed to cure, with orwithout a heat supplement, and the part or article demolded.

EXAMPLES

Resin A

Resin A is an end-capped unsaturated polyetherester resin blended withstyrene monomer. The unsaturated polyetherester resin is prepared bycharging a 5 liter flask, equipped with an agitator, condenser,thermometer and sparge tube for introducing nitrogen gas, with 1418grams ACCLAIM™ Polyol 2200 (a 2000 MW polyoxpropylene diol availablefrom ARCO Chemical Co.), 442 grams propylene glycol, 1140 grams maleicanhydride and 2.3 grams p-toluenesulfonic acid monohydrate and heatingthe mixure to 195 C. for 4 hours while introducing nitrogen gas untilthe acid number drops to 110 mg KOH/g. End-capping is conducted byreducing the temperature of the reaction mixture to 140 C., introducing260 g DCPD dropwise to the resulting mixture, and maintaining the 140 C.-temperature for 4 hours until the acid number is reduced to about 84 mgKOH/g. The mixture is then charged with 0.7 g DMP-30(2,4,6-trisdimethylaminomethylphenol), mixed and maintained at 140 C.for 5 minutes, after which 675 g EPON® Resin 828 (available from theShell Oil Co.) is added, the reaction mixture continues to be mixed andis maintained at a temperature of 140-150 C. until the acid number dropsto 30 mg KOH/g. The reaction product is blended with 1500 g styrenemonomer to form about 5,000 g of a clear resin solution containing theend-capped resin (Resin A) having a viscosity of 1100 cp (1.100 Pa.s)and 65 wt. % NVM.

Resin B

Resin B is also an end-capped unsaturated polyetherester resin blendedwith styrene monomer. The end-capped unsaturated polyetherester resin isprepared the same way as that of Resin A, except that a mixture of 520 gEPON® Resin 828 and 310 g CARDURA® E-10 Resin (a glycidyl esteravailable from Shell Oil Co.) in place of the 675 g EPON® Resin 828 ofthe Resin A procedure. The resulting end-capped unsaturatedpolyestherester resin (Resin B) is blended with styrene monomer suchthat the blend has a viscosity of 385 cp (0.385 Pa.s) and 65 wt. % NVM.

DCPD Resin

DCPD resins is a DCPD unsaturated polyester resin blended with styrene.The DCPD unsaturated polyester resin is prepared by charging a 4 literresin kettle, equipped with a mechanical stirrer, nitrogen sparge tube,thermocouple (for measuring temperature), and a distillation head, with1032 g maleic anhydride, heating the maleic anhydride to 150 F. (66 C.),slowly adding about 207 g water to the maleic anhydride and allow thetemperature to rise to about 245 F. (118 C.) due to the heat given offby the exothermic reaction between the maleic anhydride and the addedwater, and then, when the temperature begins to drop of its own accord,adding 1392 g DCPD at a rate that maintains the temperature of thereactants between about 245 and 265 F. (between about 118 C. and 129 C.)until the acid number of the reaction mixture is 245 KOH/g or less. Then415 g of ethylene glycol are added to the resulting reaction mixture andthe temperature of the reaction mixture is raised to 400 F. (204 C.) andmaintained at about that temperature until the acid number drops to 42KOH/g. A vacuum (i.e., negative pressure differential) of 25 inches Hg(85 kPa) is applied to the mixture for about 30 minutes as the reactiontemperature is allowed to cool. The reaction product is then blendedwith 1200 g styrene.

Preparation of the Curable Thermoset Resins of the Invention

Resin A and DCPD Resin are combined in the proportions shown in Table 1below to make Examples 1 and 2 of this invention. For these examples,styrene monomer is added to adjust the wt. % NVM from 65 wt. % to 60 wt.%. A catalyst system is added to cure each example at room temperature,which consists of 1.63 wt. % MEK peroxide, 0.15 wt. % cobaltnaphthenate, and 0.12 wt. % N,N-dimethylacetoacetamide. The resultsobtained are shown in Table 1 below.

TABLE 1 Result of Curing Examples 1 and 2 of the InventionComponent/Property Example 1 Example 2 Resin A 80 60 DCPD Resin 20 40 %Nonvolatile Material (NVM) 60 60 Gel Time (min.) (1.63% DDM-9 22 17(Lucidol)) Gel to Peak Exotherm (min.) 11 13 Maximum ExothermTemperature 302° F. (150° C.) 366° F. (186° C.)

Gel coated laminates are prepared by spraying a full ISO/NPG type of gelcoat on a glass mold, drawing down the gel coat to 28 and 48 mil (0.58and 1.22 mm) “wet” thickness, and then letting the gel coat cure for 1hour at ambient temperature. A skin laminate is applied to the gel coatconsisting of 2 plies of 1.5 ounce (42.5 g) fiberglass mat saturatedwith either the Example 1 or the Example 2 resin blend, as indicated inTable 2 below, such that each skin laminate had a 30 wt. % glasscontent. The cure time for skin laminate is 2 hours at ambienttemperature. The main laminate consisting 4 plies of 1.5 ounce (42.5 g)fiberglass mats with 30 wt. % glass content are applied after the skinlaminate. A typical marine grade laminate resin, STYPOL® 40-4822, isused. The laminate is cured at ambient temperature for at least 16 hoursbefore the water boil test was performed. Table 2 shows the surfaceprofile ratings.

TABLE 2 Before 100 Hours 150 Hours Example 1 Longwave, mean 1.8 64.181.8 Shortwave, mean 1.3 59.0 58.4 Rating, mean 10.4  1.7  0.5 ANSI*Rating — 4.0 — Example 2 Longwave, mean 1.2 51.2 74.1 Shortwave, mean0.8 42.5 60.3 Rating, mean 10.5  2.6  1.0 ANSI* Rating — 4.2 — *ANSIrefers to the American National Standards Institute. The “ANSI Rating”refers to a surface profile test described in the publicationANSIZ124.1-1987 section 6.3. A lower ANSI rating indicates bettersurface profile. An ANSI rating greater than 9 is considered failure.

The waviness rating values (ACT™ Orange Peel Standards) are typicalindustry visual test methods used to describe the surface appearance ofan object. A BYK-Gardner wave-scan is used to measure the surfaceappearance of various test panels. The wave-scan can report the resultsin both long-term (structure size greater than 0.6 mm) and short-termwaviness (structure size less than 0.6 mm). Both long-term andshort-term waviness are rated from 0 to 100. The higher the number, themore waviness is observed. The long-term and short-term waviness arethen mathematically correlated to a surface rating value from 0 to 10.The higher the number, the smoother the surface appears.

What is claimed is:
 1. A curable thermoset resin composition useful forimparting water and/or solvent resistance to gel coated fiber-reinforcedpolymers comprising: (A) At least 5 wt. % of an at least partiallyend-capped unsaturated polyetherester resin obtained by (1) reacting atleast one polyether, the polyether selected from the group consisitingof polyether polyols, alkylene oxide-alkylene oxide copolymers, whereinthe alkylene group of each alkylene oxide is different, and combinationsthereof, and at least one ethylenically unsaturated anhydride ordicarboxylic acid in the presence of at least one catalyst effective topromote insertion of the anhydride or dicarboxylic acid intocarbon-oxygen bonds of the polyether to produce unsaturatedpolyetherester resin polymer chains and (2) reacting the unsaturatedpolyetherester resin polymer chains with at least one end-cappingcompound to form the at least partially end-capped polyetherester resin,wherein the at least one end-capping compound comprises at least onecompound having at least one epoxy group; (B) an unsaturated polyesterresin having a ratio of the number average molecular weight to theaverage number of double bonds per polymer molecule in the range fromabout 200 to about 400, in an amount such that the weight ratio ofpolyester resin (B) to polyetherester resin (A) is in the range fromabout 10:90 to about 90:10; (C) about 10 to about 70 wt. % of at leastone vinyl monomer; and (D) a curing agent.
 2. The composition accordingto claim 1, wherein the at least one compound having at least one epoxygroup is a compound having the formula:

wherein R¹, R², and R³ represent a hydrogen atom or a hydrocarbyl groupoptionally having one or more hetero atoms, provided that at least oneof R¹, R², and R³ is not a hydrogen atom.
 3. The composition accordingto claim 1, wherein the compound having at least one epoxy group has anumber average molecular weight less than or equal to
 500. 4. Thecomposition according to claim 3, wherein the at least one compoundhaving at least one epoxy group is a reaction product of epichlorohydrinand bisphenol-A.
 5. The composition according to claim 1, wherein the atleast one end-capping compound has been added until the acid number ofthe end-capped unsaturated polyetherester (A)(2) is less than about 50percent of the acid number of the unsaturated polyetherester (A)(1)prior to end-capping.
 6. The composition according to claim 1, whereinthe unsaturated polyester resin (B) is derived from at leastdicyclopentadiene, an unsaturated carboxylic acid anhydride, and aglycol.
 7. The composition according to claim 1, wherein the vinylmonomer (C) is styrene.
 8. The composition according to claim 1, whereinthe curing agent (D) comprises a free radical initiator and anaccelerator.
 9. The composition according to claim 1, wherein the atleast partially end-capped unsaturated polyetherester has a viscositynot greater than 1500 cp and is present in an amount from about 10 wt. %to about 80 wt. %, and the weight ratio of polyester resin (B) topolyetherester resin (A) is in the range from about 25:75 to about75:25.
 10. An intermediate for making a skin laminate comprisingreinforcing fibers and the curable thermoset resin composition accordingto claim 1 in the form of a sheet having a cross-sectional thicknessless than 1 percent of its total surface area.
 11. An intermediate formaking a skin laminate comprising reinforcing fibers and the curablethermoset resin composition according to claim 9 in the form of a sheethaving a cross-sectional thickness less than 1 percent of its totalsurface area.
 12. A fiber-reinforced polymer composite obtained bycombining a curable thermoset resin composition according to claim 1with reinforcing fiber and curing the curable thermoset resincomposition.
 13. A method for making a curable thermoset resincomposition comprising combining: (A) At least 5 wt. % of an at leastpartially end-capped unsaturated polyetherester resin obtained by (1)reacting at least one polyether, the polyether selected from the groupconsisiting of polyether polyols, alkylene oxide-alkylene oxidecopolymers wherein the alkylene group of each alkylene oxide isdifferent, and combinations thereof, and at least one ethylenicallyunsaturated anhydride or dicarboxylic acid in the presence of at leastone catalyst effective to promote insertion of the anhydride ordicarboxylic acid into carbon-oxygen bonds of the polyether to produceunsaturated polyetherester resin polymer chains and (2) reacting theunsaturated polyetherester resin polymer chains with at least oneend-capping compound to form the at least partially end-cappedpolyetherester resin, wherein the at least one end-capping compoundcomprises at least one compound having at least one epoxy group; (B) Anunsaturated polyester resin having a ratio of the number averagemolecular weight to the average number of double bonds per polymermolecule in the range from about 200 to about 400, in an amount suchthat the weight ratio of polyester resin (B) to polyetherester resin (A)is in the range from about 10:90 to about 90:10; (C) About 10 to about70 wt. % of at least one vinyl monomer; and (D) A curing agent.